The invention belongs to the field of pharmacy, and relates to a new marine natural product Largazole amide analogue, a preparation method thereof and application of a drug containing the compound or a composition thereof as an antitumor therapeutic agent. The invention provides a compound represented by a general formula (I) or a salt thereof, and an antitumor drug composition containing the compound or the salt thereof of a therapeutically effective dose and a pharmaceutical carrier. The compound has a more powerful effect of inhibiting proliferation of tumor cells as compared with a clinically used drug SAHA. The drug can be used for treating solid tumors, cancer, lymphomas, Hodgkin diseases, tumor diseases, new growing tumor diseases or the like. The general formula (I) is shown in the specification.